The present invention relates to a method and to a device for evaluating sensor signals from a seat mat in a vehicle seat.
K. Brillen, L. Federspiel, P. Schockmehl, B. Serban, and W. Sherrill, xe2x80x9cOccupant Classification System for Smart Restraint Systems,xe2x80x9d SAE paper 1999, pp. 33-38, describes pressure sensors, which are used in a seat mat for a vehicle seat and are arranged in a matrix. In response to increased resistance, the pressure sensors have reduced electrical resistance. In this context, the pressure sensors can be divided into active and inactive matrix elements. From these matrix elements, a seat profile can be generated, so as to determine features for classifying the passengers.
In contrast, the method and the device according to the present invention for evaluating sensor signals from a seat mat in a vehicle seat have the advantage that the sensors are divided in binary fashion into active and inactive sensors. This arrangement has the advantage that the sensor signals are easier to process, the processing hardware may be more easily configured, because only binary information has to be processed from the sensors in the seat mat and not absolute values, and a nonlinear relationship between the pressure exerted and the measured resistance value of the sensor is insignificant. Another advantage is that the calibration of the seat mat is highly simplified because only a threshold value has to be determined. The pressure-sensitive sensors in the seat mat may be configured more simply because the absolute resistance values no longer have meaning. In addition, the device according to the present invention may be robust with respect to dispersions in the production process, because the threshold may be set using software. In addition, the device according to the present invention is less susceptible to disturbance with regard to production and operating conditions.
Advantageous improvements of the method and the device according to the present invention are possible for evaluating sensor signals from a seat mat in a vehicle seat.
The threshold value which distinguishes between active and inactive sensors may be set as a function of the installation of the seat mat in the vehicle seat. Therefore, it is possible to take into account the individual installation conditions and varying seat designs. This leads to increased precision in the measured sensor activity.
On the base of the active and inactive sensors, a seat profile may be generated which makes possible a weight classification of the person sitting on the vehicle seat. In this context, it is specifically possible to establish whether it is a person or an object and whether the person is large, small, heavy, or light.
The processor of the device according to the present invention may be connected to a restraint system and in the process specifically to a control unit of the restraint system, in order to transmit the weight classification to the control unit. Thus, it is possible to trigger an air bag in an improved manner as a function of the person. If an object, for example, a box, is detected on the vehicle seat, then the air bag is not triggered for this vehicle seat.